1. Field of the Disclosure
The present invention relates to liquid crystal display devices, and more particularly, to a back light unit for a liquid crystal display device, which can improve safety and reliability of the back light unit; and a method for fabricating the same.
2. Discussion of the Related Art
In general, the liquid crystal display device displays an image on a screen as a transmission rate of a light beam is controlled in response to a signal applied to a matrix of control switches. Since the liquid crystal display device can not emit the light, the liquid crystal display device requires an additional light source, such as the back light unit.
In the back light units, there are a direct lighting type and an edge lighting type depending on a position of the light source. The edge lighting type back light unit has the light source mounted to one side edge of the liquid crystal display device for directing the light from the light source to a liquid crystal display panel through a light plate and a plurality of optical sheets. The direct lighting type back light unit has a plurality of light sources under the liquid crystal display device for directing the light from the light sources to a liquid crystal display panel through a diffusion plate and a plurality of optical sheets. Currently, the direct lighting type back light unit having brightness, light uniformity, and color purity better than the edge lighting type back light unit is used more than the edge lighting type back light unit, mostly for LCD TV.
The back light unit includes a plurality of lamps, a cover bottom, a diffusion plate, a plurality of optical sheets, a PCB (Printed Circuit Board) having sockets formed thereon for placing the plurality of lamps therein, and an inverter circuit unit for supplying an AC high voltage to the lamps through the sockets.
The PCB is fastened to the cover bottom with conductive screws. There are frequent occasions when sparks take place between the screws and sockets. In more detail, in order to fasten the PCB to an inside space of the cover bottom rigidly, high strength conductive screws are used. However, if securing safe distances between the conductive screws and the sockets fail due to various reasons, such as variation of assembly between the PCB and the cover bottom, degradation of the conductive screw during operation of the back light unit, or so on, the sparks take place between the conductive screws and the sockets. As a result of this, problems in safety and reliability of the back light unit, such as failure of regular lighting of the lamps, and the like, take place.